Local community

Very difficult- I was thinking this myself.
I guess the easiest way would be to talk to the people you meet when out playing, although I tend not to do that in case other people just want to be left alone.

I think the most successful groups have members who probably know each other already and are families or neighbors.

I swear that red team in my area must have a WhatsApp group because they often have 7 plus people all work together to destroy a gym and prestige a new one.

Anyways, I am impressed by their ability to all be in the same place at the same time.

We made some telegram group, one for all player plus every team has it's own and every time we find a new player we add him. Because of this we farm together and we know each other and very few people left the game.

My university has a pokemon go club and that seems to be a great way. I also would suggest Facebook groups.

Ive been thinking about this as well. I hung up a sign near a gym with my name for Line App. Just hung it up yesterday so nobody has joined yet. Im trying to put together a crew to meet 2x a week to take down spoofer gyms in my area.

If you want to know how many ppl playing pokemon in your area just use lure module for a few day. Btw I'm still wonder about the lure purpose, it is for lure pokemon or ppl actually.

Go to the next biggest city, there will be a place where trainers meet to lure several stops day by day.
In my city is a place where four stops was always lured. But now in winter this place is kind of dead. Because it is too cold outside.
Between summer and fall I get close to some of them exanging phone numbers, having team dependent whats app groups and meeting several times a week. Even our "villagers" visit us almost every two weaks.

I could never imaging playing this game solo.